1. Technical Field
The invention relates to text input technology. More specifically, the invention relates to text entry solutions to wireless communication devices with limited keypads.
2. Description of the Prior Art
For many years, portable computers have been getting smaller and smaller. The principal size-limiting component in the effort to produce a smaller portable computer has been the keyboard. If standard typewriter-size keys are used, the portable computer must be at least as large as the keyboard. Miniature keyboards have been used on portable computers, but the miniature keyboard keys have been found to be too small to be easily or quickly manipulated by a user. Incorporating a full-size keyboard in a portable computer also hinders true portable use of the computer. Most portable computers cannot be operated without placing the computer on a flat work surface to allow the user to type with both hands. A user cannot easily use a portable computer while standing or moving.
In the latest generation of small portable computers, called Personal Digital Assistants (PDAs), companies have attempted to address this problem by incorporating handwriting recognition software in the PDA. A user may directly enter text by writing on a touch-sensitive panel or screen. This handwritten text is then converted by the recognition software into digital data. Unfortunately, in addition to the fact that printing or writing with a pen is in general slower than typing, the accuracy and speed of the handwriting recognition software has to date been less than satisfactory.
Presently, a tremendous growth in the wireless industry has spawned reliable, convenient, and very popular mobile communications devices available to the average consumer, such as cell phones, two-way pagers, PDAs, etc. These handheld wireless communications and computing devices requiring text input are becoming smaller still. Recent advances in two-way paging, cellular telephones, and other portable wireless technologies have led to a demand for small and portable two-way messaging systems, and especially for systems which can both send and receive electronic mail (“e-mail”). Some wireless communications device manufacturers also desire to provide to consumers devices with which the consumer can operate with the same hand that is holding the device.
Disambiguation Background.
Prior development work has considered use of a keyboard that has a reduced number of keys. As suggested by the keypad layout of a touch-tone telephone, many of the reduced keyboards have used a 3-by-4 array of keys. Each key in the array of keys contains multiple characters. There is therefore ambiguity as a user enters a sequence of keys, since each keystroke may indicate one of several letters. Several approaches have been suggested for resolving the ambiguity of the keystroke sequence, referred to as disambiguation.
One suggested approach for unambiguously specifying characters entered on a reduced keyboard requires the user to enter, on average, two or more keystrokes to specify each letter. The keystrokes may be entered either simultaneously (chording) or in sequence (multiple-stroke specification). Neither chording nor multiple-stroke specification has produced a keyboard having adequate simplicity and efficiency of use. Multiple-stroke specification is inefficient, and chording is complicated to learn and use.
Other suggested approaches for determining the correct character sequence that corresponds to an ambiguous keystroke sequence are summarized in the article “Probabilistic Character Disambiguation for Reduced Keyboards Using Small Text Samples,” published in the Journal of the International Society for Augmentative and Alternative Communication by John L. Arnott and Muhammad Y. Javad (hereinafter the “Arnott article”). The Arnott article notes that the majority of disambiguation approaches employ known statistics of character sequences in the relevant language to resolve character ambiguity in a given context.
Another suggested approach based on word-level disambiguation is disclosed in a textbook entitled Principles of Computer Speech, authored by I. H. Witten, and published by Academic Press in 1982 (hereinafter the “Witten approach”). Witten discusses a system for reducing ambiguity from text entered using a telephone touch pad. Witten recognizes that for approximately 92% of the words in a 24,500 word dictionary, no ambiguity will arise when comparing the keystroke sequence with the dictionary. When ambiguities do arise, however, Witten notes that they must be resolved interactively by the system presenting the ambiguity to the user and asking the user to make a selection between the number of ambiguous entries. A user must therefore respond to the system's prediction at the end of each word. Such a response slows the efficiency of the system and increases the number of keystrokes required to enter a given segment of text.
H. A. Gutowitz, Touch-Typable Devices Based on Ambiguous Codes and Methods to Design Such Devices, WO 00/35091 (Jun. 15, 2000) discloses that the design of typable devices, and, in particular, touch-type devices embodying ambiguous codes presents numerous ergonomical problems and proposes some solutions for such problems. Gutowitz teaches methods for the selection of ambiguous codes from the classes of strongly-touch-typable ambiguous codes and substantially optimal ambiguous codes for touch-typable devices such as computers, PDA's, and the like, and other information appliances, given design constraints, such as the size, shape and computational capacity of the device, the typical uses of the device, and conventional constraints such as alphabetic ordering or Qwerty ordering.
Eatoni Ergonomics Inc. provides a system called WordWise, (Copyright 2001 Eatoni Ergonomics Inc.), adapted from a regular keyboard, and where a capital letter is typed on a regular keyboard, and an auxiliary key, such as the shift key, is held down while the key with the intended letter is pressed. The key idea behind WordWise is to choose one letter from each of the groups of letters on each of the keys on the telephone keypad. Such chosen letters are typed by holding down an auxiliary key while pressing the key with the intended letter. WordWise does not use a vocabulary database/dictionary to search for words to resolve ambiguous, unambiguous, or a combination thereof entries.
Zi Corporation teaches a predictive text method, eZiText® (2002 Zi Corporation), but does not teach nor anywhere suggest explicit text filtering in ambiguous mode,nor in combination with 2-key explicit entry, stem-locking, or n-gram searches.
A Need for Improvements to Current Disambiguation Methodologies.
Disambiguating an ambiguous keystroke sequence continues to be a challenging problem. A specific challenge facing disambiguation is providing sufficient feedback to the user about the keystrokes being input. With an ordinary typewriter or word processor, each keystroke represents a unique character which can be displayed to the user as soon as it is entered. But with word-level disambiguation, for example, this is often not possible, because each entry represents multiple characters, and any sequence of entries may match multiple objects, such as, words or word stems, for example. Such ambiguity is especially a problem when, for example, the user makes a spelling or entry error and the user is not certain of such error until the complete sequence is entered and the desired result is not presented. In another example, previous systems utilizing word-level disambiguation fail to provide any feedback until a predetermined selection, such as a specific key selection, is made that is recognizable by the system as a termination selection, e.g. the space key.
Moreover, some alphabets, such as Thai and Arabic, contain more letters than the alphabet for English, which leads to even greater ambiguity on a reduced number of keys. Efficient input of these languages demands a mechanism for reducing that ambiguity when needed.
Therefore, it would be advantageous to provide a disambiguating system which reduces the apparent ambiguity on the display during entry and improves the user's ability to detect and correct spelling and/or entry errors.
It would also be advantageous to provide a disambiguating system which reduces ambiguity and increases efficiency by providing explicit filtering capabilities such that a list of candidate words, word stems, sequence of symbols, and the like, is narrowed, and the user can subsequently be offered a word completion or sequence completion quicker. More specifically, it would be advantageous to allow locking in a current state of interpretation of a part of or all of previously entered characters including, but not limited to an object and/or word stems, and explicitly entered characters, thereby preventing reinterpretation of previous entries.
It would also be advantageous to build around explicitly entered characters as anchors, for the end of or beginning of new objects, words, or word stems.
It would also be advantageous to offer reasonable guesses for extending objects or words by n-gram analysis of preceding explicitly entered characters.
It would also be advantageous to reduce ambiguity and increase efficiency during the process of disambiguating a linguistic object, such as a word or word stem, for example, by preventing reinterpretation of previous entries.
It would also be advantageous to recognize common delimiters entered ambiguously or explicitly as suggesting a point connecting two separate sets of characters to suggest where the interpretation of keystrokes could be restarted.